I've never bred dumerils so I'm no expert but I dug up some weather links for Madagascar that you may find interesting. I never realized it got so cool there, down into the 50s some months and not much past low 80s ever. I would think you could drop your girl down to 78-80 but will let others who actually has bred them chime in 
Good luck with her, she looks massive and beautiful!
http://www.worldtravelguide.net/country/155/climate/Africa/Madagascar.html
http://www.bbc.co.uk/weather/5day.shtml?world=1022
http://www.bbc.co.uk/weather/world/country_guides/results.shtml?tt=TT000340
http://www.studentsoftheworld.info/pageinfo_pays.php3?Pays=MAD&Opt=climate
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Ken Roshak
BlackSwampSerpents@toast.net

